injection/pulsed neutron log

An in-situ recording in which a material with high neutron-capture cross section is injected into the flowstream of a production or injection well to determine fluid paths and velocities. The material used is normally borax or water with high salinity, both of which cause a significant increase in the capture cross section measured by a pulsed-neutron log. In the most common application, the material is injected across the producing intervals of a production well. By comparing pulsed neutron logs recorded before and after injection, the injectivity, and hence productivity, of each interval can be estimated. Any cement channels or leaks will also be observed.